{"id":"CVE-2026-90269","summary":"bpf: Reject load-acquire from pointers requiring fault protection","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Reject load-acquire from pointers requiring fault protection\n\nA BPF_LOAD_ACQ is not rewritten to a BPF_PROBE_MEM load by the verifier,\nunlike a regular BPF_LDX, so the JIT emits a plain load with no exception\ntable entry and a fault panics the kernel instead of being handled.\n\nReject the source pointer types that a BPF_LDX would have had that fault\nprotection applied to, i.e. the ones bpf_convert_ctx_accesses() turns\ninto BPF_PROBE_MEM: a bare PTR_TO_BTF_ID, PTR_TO_BTF_ID | PTR_UNTRUSTED,\nPTR_TO_BTF_ID | MEM_ALLOC | PTR_UNTRUSTED and PTR_TO_MEM | MEM_RDONLY |\nPTR_UNTRUSTED.\n\nThis is reachable e.g. by loading -\u003emm out of a trusted task_struct\nyields an untrusted pointer to mm_struct, and it is NULL for a kernel\nthread:\n\n  [...]\n  SEC(\"tp_btf/sched_switch\")\n  int BPF_PROG(demo, bool preempt, struct task_struct *prev,\n               struct task_struct *next)\n  {\n      struct mm_struct *mm = next-\u003emm;  /* untrusted */\n\n      out_ldx = (__u64)mm-\u003epgd;         /* BPF_LDX      */\n      out_acq = load_acquire(&mm-\u003epgd); /* BPF_LOAD_ACQ */\n      return 0;\n  }\n  [...]\n\nBoth dereference the same pointer, but only the BPF_LDX is protected\n(x86-64 JIT, jump targets shown prog-relative):\n\n  [...]\n  ; out_ldx = (__u64)mm-\u003epgd;\n  17:   movq    $-10485760, %r10\n  1e:   movq    %rsi, %r11\n  21:   addq    $184, %r11\n  28:   subq    %r10, %r11\n  2b:   movabsq $140737498841088, %r10\n  35:   cmpq    %r10, %r11\n  38:   ja      0x3e                 \u003c-- kernel addr?\n  3a:   xorl    %edi, %edi           \u003c-- no: dst = 0, skip the load\n  3c:   jmp     0x45\n  3e:   movq    184(%rsi), %rdi      \u003c-- yes: load + extable entry\n  [...]\n  ; load_acquire(&mm-\u003epgd)\n  53:\tmovq    %rsi, %rdi\n  56:\tmovq    184(%rdi), %rax       \u003c-- no check, no extable entry\n  [...]\n\nNote that BPF_PROBE_MEM is not visible in a bpftool xlated dump, as\nbpf_insn_prepare_dump() rewrites it back to BPF_MEM.\n\nA PTR_TRUSTED pointer is deliberately not on the list. Such a load is\nnot converted either, but it does not need to be, since the pointer is\nguaranteed live, so load-acquire from it stays allowed.\n\nThe check is gated on BPF_LOAD_ACQ so that atomic RMW and store-release\nerror messages are unchanged; writes (RMW / store-release) to such\npointers are already rejected elsewhere, so only load-acquire needs this.","modified":"2026-09-19T03:47:28.768092784Z","published":"2026-09-17T16:08:03.996Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90269.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/5f8ade6e9b7931fc9697394f1b2c4ae833f5ac18"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7db0a00445f1a40bacfe9b747405c11cb5f10fc9"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c4c8de3bf48d3756ab0f910fe5cc4937d70efdcd"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90269.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-90269"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"880442305a3908589bf4d6fc1d79edb577ee497c"},{"fixed":"c4c8de3bf48d3756ab0f910fe5cc4937d70efdcd"},{"fixed":"5f8ade6e9b7931fc9697394f1b2c4ae833f5ac18"},{"fixed":"7db0a00445f1a40bacfe9b747405c11cb5f10fc9"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90269.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.15.0"},{"fixed":"6.18.52"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.6"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90269.json"}}],"schema_version":"1.9.0"}